Steering Shaft Profile Sleeve Locking With Integral Projection
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Solution Overview
Problem
Existing steering shaft designs face issues with the fixation of profile sleeves due to differing thermal expansion coefficients of materials, leading to constrained states and high production costs associated with complex attachment mechanisms.
Innovation Solution
The profile sleeve is secured on the inner shaft with a one-piece integral projection that engages with an opening, allowing for axial displacement and torque-locking, while minimizing production costs and thermal expansion issues by using a design where the projection and inner shaft are a single component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If locking lugs are used to fix the profile sleeve to the inner shaft, then the profile sleeve is secured in the axial direction, but the profile sleeve becomes stressed during temperature changes due to different coefficients of thermal expansion
Solution Approach 1:
The harmful constraint is removed by eliminating the locking lugs that caused thermal stress. Instead, the profile sleeve is fixed to the inner shaft through a press fit connection that allows for thermal expansion without creating constrained conditions, while still maintaining reliable axial fixation through the interference fit between the profiled outer surface of the inner shaft and the corresponding profiled inner surface of the profile sleeve.
Solution Approach 2:
The connection parameters are changed from rigid mechanical locking (locking lugs) to elastic-deformable press fit connection. The profiled surfaces are designed with specific geometric parameters that enable the profile sleeve to be pressed onto the inner shaft with controlled interference, allowing thermal expansion while maintaining fixation reliability.
2Reliability
If a projection is attached to the inner shaft to fix the profile sleeve, then the profile sleeve is secured in position, but a disadvantageously high manufacturing effort results
Solution Approach 1:
The separate projection component is merged with the inner shaft by integrating the fixation function directly into the profiled outer surface of the inner shaft. The profiled geometry itself serves as the fixation mechanism, eliminating the need for additional attached projections and reducing manufacturing steps while maintaining position fixation reliability.
Solution Approach 2:
The profiled outer surface of the inner shaft serves multiple functions simultaneously: it provides torque transmission through the profiled engagement with the profile sleeve, enables axial fixation through press fit interference, and eliminates the need for separate attachment components. This multi-functionality reduces manufacturing complexity while maintaining fixation reliability.
Data Source
Figure 1~2
Figure 3~5
Figure 6
AI summary
The invention relates to a steering shaft (1) for a motor vehicle having an inner shaft (3), an outer shaft (5), and a profile sleeve (4) which is arranged on the inner shaft (3) and is fixed hereon in such a way that the inner shaft (3) together with the profile sleeve (4) is displaceable in the axial direction relative to the outer shaft (5), wherein the inner shaft (3) and the outer shaft (5) are coupled in a torque-conducting manner with the profile sleeve (4) arranged in-between. The profile sleeve (4) has an aperture (19) in which a protrusion (20) arranged on an outer surface of the inner shaft (3) securely engages the profile sleeve (4) in its position on the inner shaft (3) at least in the axial direction. The invention also relates to a method for producing a steering shaft (1) for a motor vehicle.